The lipopolysaccharide of Citrobacter freundii O22 (strain PCM 1555) was
degraded under mild acidic conditions and the O-polysaccharide released was isolated by
gel chromatography. Sugar and methylation analyses along with 1H- and 13C-NMR
spectroscopy, including two-dimensional 1H,1H ROESY and 1H,13C HMBC experiments,
showed that the repeating unit of the O-polysaccharide has the following structure:

a-Abep(1
|
3
->2)-a-D-Manp-(1->4)-a-L-Rhap-(1->3)-a-D-Galp-(1->

where Abe is abequose (3,6-dideoxy-D-xylo-hexose).
SDS-PAGE and immunoblotting revealed that the O-antigen of C. freundii O22 is
serologically identical to those of Salmonella group B serovars (Typhimurium,
Brandenburg, Sandiego, Paratyphi B) but not related to other abequose-containing O-antigens
tested (Citrobacter werkmanii O38 and Salmonella Kentucky) or colitose
(L enantiomer of abequose)-containing O-antigen of Escherichia coli O111.